It is known to provide a coupling socket, which can be connected to a first line and receives a coupling plug of a second line in sealed fashion; a closing valve located in the coupling socket is intended to be kept open by the inserted coupling plug. Locking devices are located on the coupling socket, each having at least one locking element for the inserted coupling plug. A slider sleeve, supported axially displaceably on the coupling socket counter to spring force and cooperating with the two locking devices, is provided; it is manually actuatable and can be displaced counter to spring force, from an outset position in which the coupling plug is kept in its coupling position by a first locking device, when the valve is open, to a first position in which the coupling plug is kept in an intermediate position by the second locking device, when the valve is closed. A venting device is operative for the second line. The slider sleeve can then be displaced from this first position in the same direction onward to a second position, in which the coupling plug is completely released.
Various versions of rapid connection-release coupling with these characteristics are known, for instance from German Patent Specifications 19 02 986, 19 43 552, 22 26 793, and 27 05 319. The essential property of this self-venting coupling is that provisions are made to counteract the danger to the user upon uncoupling, caused by the fact that when the coupling is loosened, the pressurized gas in the uncoupled line is released and escapes through the coupling plug. Even with relatively small cross sections and lengths of the uncoupled line, uncoupling causes a sudden whiplike motion of the line that endangers the user. The danger of injury to the user is all the greater unless unintentional uncoupling of the line is reliably precluded.
The known rapid connection-release coupling is therefore designed in such a way that for uncoupling, the user should first advance the slider sleeve to a first position, in which only the first locking device that has held the coupling plug in its sealed coupling position is release. The coupling plug can enter an intermediate position in the coupling socket by traveling only a relatively short distance, which is longer than the stroke of the valve, and is securely locked in this intermediate position by the second locking device. In this intermediate position, with the valve closed, the coupling plug communicates with the ambient air via a venting device in the form of conduits or annular gaps in the coupling socket, so that venting of the line connected to it can proceed as long as the coupling plug is still firmly held in the coupling socket. Only once the venting has been done should the user displace the slider sleeve from the intermediate position to a final position, in the same direction as in the previous motion from the outset position to the intermediate position; in the final position, the second locking device is also released, so that the coupling plug is completely released. Variably dimensioning the spring characteristics of spring means intended for biasing the slider sleeve toward its outset position, for instance, provides a locking threshold for the slider sleeve, so that increased displacement force is required from the user if he wishes to shift the slider sleeve out of the intermediate position into the final position. The user can arbitrarily overcome this locking threshold and thus in a single gesture shift the slider sleeve from its outset position to the final position, or from the intermediate position to the final position, before venting has been completed; hence with this rapid connection-release coupling, the release of the coupling plug before the line connected to it has been sufficiently well vented cannot be precluded, with the attendant danger to the surroundings from the released coupling plug and the whipping line. Moreover, the user can essentially perceive the completion of the venting process only acoustically, from the cessation of the noise produced by the gas as it emerges under pressure.
The same is basically true of a pipe coupling known from European Patent Specification 0 013 393 B1, to which U.S. Pat. No. 4,366,945, Blauenstein, corresponds, in which the arrangement is such that for uncoupling, the slider sleeve is first pushed back from its outset position into a first position, in which the coupling plug can move to an intermediate position for venting, from which the coupling plug is then released by moving the slider sleeve, held in its intermediate position by resilient detent means, back in the opposite direction into its outset position. Once again, by an arbitrary rapid displacement of the slider sleeve back and forth, the user can release the coupling plug from the coupling socket immediately, independently of the venting process. Particularly with overhead work, the coupling plug might unintentionally be spun out of the coupling socket if the slider sleeve is unintentionally shifted back and forth.